The flax plant Linum usitatissimum comprises a stem of 60 to 80 cm according to strain and growth. The stem is reinforced by strong fibre bundles for providing a sufficient rigidity, said fibre bundles extending from the root to the top of the plant. The fibre bundles are arranged outermost in the reed of the stem, and the spaces between the fibre bundles have been filled with ligneous cellulosis, which provides the so-called shives after the flax stem has been processed to separate the fibres.
In order to separate the long flax fibres from the xylem of the stem, the flax must be subjected to a so-called retting after the harvesting, said retting being a microbiological process. Today it is, however, possible to replace the conventional and rather uncertain retting process with a retting in water admixed enzymes. The water retting causes a decomposition of the hemicellulosis and pectine binding the fibres together as well as binding the fibres to the xylem like an adhesive.
By the conventional retting, the microorganisms supply the enzymes, said retting usually taking place in two different ways: Water retting and dew retting. The dew retting is the most interesting process in the present connection, and it takes place when the cut stems are lying in the fields after the harvesting. The water retting takes place in lakes or streams where the sheaves of flax have been placed, but due to the pollution of the streams the water retting has been forbidden in many places.
In principle, all the above three retting processes can be used in connection with production of fibres provided they take place in a suitable manner. The resulting fibres can by way of a further processing be used for the manufacture of plates of flax fibres according to the invention. The water retting can take place in closed reservoirs optionally containing enzymes as described in Danish Patent Application No. 4757/86.
By the conventional production of flax, the stems are subjected to a retting and drying followed by a number of mechanical processings with the result that the flax fibre bundles are separated from the shives. The flax fibres are very strong, and their length is substantially the same after the separation from the shives as in the stems. A small amount of the fibres is destroyed during the processing partly due to an overretting and partly due to the mechanical processing, and these fibres are separated and sold as flax tow. Unlike the first-rate fibres which are processed while arranged in parallel in bundles, the flax tow fibres are randomly arranged relative to one another. However, the flax tow still comprises fibres of a considerable length and cannot therefore be processed by means of conventional textile machines, such as machines for the processing of cotton and wool.
It is not possible to manufacture a plate of flax fibres directly from flax fibres by the conventional processing in needling machines because such flax fibres are too long and too smooth. Attempts have been made at manufacturing a plate of flax fibres by needling (as described in Example 1) such fibres shortened by way of cutting, but without success.
A complete wetting followed by a chemical treatment allows the flax fibres to be separated into so-called single fibres, i.e. singlecelled fibres resembling cotton. The process is called a cottonizing, but the resulting smooth short fibres are not suited for the manufacture of plates of flax fibres by way of needling.